67 GTX 440 CARB HELP

[XMAN JR]

Before my dad passed he rebuilt the carb for the 67 GTX 440. I took it for a test drive this weekend. Runs real good. The carb works good but when you kick in the other two barrels it stumbles, from a dead stop or even driving at low RPMs. Now the motor isn't stock. It has some head work & has a larger than stock cam. Without looking the cam is under 500 lift. I want to keep the car stock looking as much as possible. Any ideas ? Should I get it rebuilt again, buy a edelbrock

 

[Bill Monk]

What carb are you running? Also, do you mean it completely falls on it's face or there is a momentary bog?

 

[Don Frelier]

It's almost a sure bet that it's too lean. It will likely want quicker timing advance as well.
The original was probably an AFB. You will need a carter strip kit. I would start with an accelerator pump cluster that is larger. Then a richer step up rod. Then primary jet size. Next secondary jet size. You can find tuning manuals online. An air fuel ratio gauge would really help when you start tinkering with it

 

[XMAN JR]

What carb are you running? Also, do you mean it completely falls on it's face or there is a momentary bog?

Not sure I think AFB I remember my dad saying it is the original type of carb that came on them. No bog falls flat on its face

 

[XMAN JR]

It's almost a sure bet that it's too lean. It will likely want quicker timing advance as well.
The original was probably an AFB. You will need a carter strip kit. I would start with an accelerator pump cluster that is larger. Then a richer step up rod. Then primary jet size. Next secondary jet size. You can find tuning manuals online. An air fuel ratio gauge would really help when you start tinkering with it

Messed with timing & got that dialed in. Would have to find someone to work on the carb. I don't know much about them. If it is gona cost me a lot I would sooner buy a new one.

 

[Don Frelier]

Did the timing advance OK when you raised the RPM?
You could do a quick check to see if the accelerator pump is working OK.
Remove the air cleaner and give the throttle a good quick shot while looking at the front center. You can do it with the engine off, just a couple times or you risk flooding. You should see two solid jets of fuel. I believe there are three possible pump lever arm settings (holes for the linkage) these can be changed from the exterior. I would not recommend the edelbrock replacement carb, they don't seem to be as good as the Carter variety.
Don't give up on the stock carb, see if you can find someone local to help. The AFB is the easiest carb to work on and should work well.

 

[XMAN JR]

Did the timing advance OK when you raised the RPM?
You could do a quick check to see if the accelerator pump is working OK.
Remove the air cleaner and give the throttle a good quick shot while looking at the front center. You can do it with the engine off, just a couple times or you risk flooding. You should see two solid jets of fuel. I believe there are three possible pump lever arm settings (holes for the linkage) these can be changed from the exterior. I would not recommend the edelbrock replacement carb, they don't seem to be as good as the Carter variety.
Don't give up on the stock carb, see if you can find someone local to help. The AFB is the easiest carb to work on and should work well.

Yep timing wise everything is great. Im not sure what the CFM of the carb is. The motor was not built stock. I will probably need a bigger CFM carb.

 

[Don Frelier]

It's not running poor because the carb is too small. It's just not set up correctly. A 625 cfm carb should run well to 5000rpm.

 

[67 GTX]

If it is the original carb, it's either a 4326s or 4327s. I think their size is somewhere around 725? Don't quote me on that please.
Without knowing more about the cam, that carb could be fine for your motor, especially if you want to keep the stock look.

 

[hoover]

There is a check ball under the accelerator pump nozzle. Might be sticking .

 

[XMAN JR]

Thanks to all. I bought a 750 cfm eddy carb. Made a big difference.